Document embedded security features deter counterfeiting of valuable papers, important records, or financial instruments such as checks, currency, so that unauthorized copies of these documents can be readily distinguished from the originals. The printing of such original documents can be done either in black-and-white (B&W) or in color, and if in color, either in spot color, colored backgrounds and/or multicolor printing. Multiple colors are often preferred for original documents for aesthetic value and ease of recognition, as well as protection from copying by conventional means. The common printing processes of valuable originals, whether in B&W or in color, are intaglio (e.g., gravure), offset printing, among others. These and the other processes mentioned in this application are very well known in the art and will not be discussed in great detail.
One approach to deterring counterfeiting or other unauthorized reproduction of originals includes embedding of “latent images” often containing covert information or other indicia within the original documents. The latent images are intended to be practically invisible to the naked eye under normal viewing conditions, particularly as being indistinguishable from a visually integrated setting in which they are embedded. However, the latent images are otherwise distinguishable through the use of a visual aid, such as a magnifier. The latent images can be arranged to disappear from copies or to become more pronounced. That is, either the absence of the latent image or the visible presence of the latent image can be construed as an indication of a non-original document.
Another approach to deterring counterfeiting includes the use of UV and IR inks to create images that only appear when illuminated by UV or IR light. UV inks have been used on documents, such as banknotes, to provide an additional indication of authenticity when illuminated by UV light.
Other developments for purposes of providing document protection are disclosed in the patent literature, as for example, in U.S. Pat. No. 5,018,767 issued May 28, 1991; U.S. Pat. No. 5,193,853 issued Mar. 16, 1993; and U.S. Pat. No. 3,675,948 issued Jul. 11, 1972; and U.S. Pat. No. 4,143,967 issued Mar. 13, 1979, all to Ralph C. Wicker. All of these patents disclose various means for providing methods and products to enable copies of documents to be distinguished from the originals, as for example, by a “large dot-small dot pattern”, a “close line-spaced pattern”, and images or indicia which are screen printed at minutely varied spaces and/or angles on the originals and are intended to produce a highly visible moiré pattern effect on the unauthorized copies. In this specification, the words “print”, “printed” and “printing” are used to refer to the making of an original document by any of a number of known printing means, including transferring images from one source to another, typically a paper medium, using a transfer agent such as ink or toner. The words “copy” and “copying” are used to refer to making copies from an original printed document.
Efforts to thwart anti-counterfeiting measures also continue to advance. The invention among its objectives is directed to providing compound document security features including one or more additional layers of protection. A need also exists to provide fast and accurate authentication of such documents.